I do hope the block heater is as magical as it's been made out to be haha.

Yeah, read around for some member's experience with the heaters.

Here's 3dplane's detailed results on using a block heater.

Originally Posted by 3dplane

I left the block heater plugged in over night. I figured it consumes about 30 cents worth of electricity doing that.
But in the morning I had frost on the roof of my house even though ambient temp was supposedly around 40°F.

I keep a small scanner in the glove box and I plugged it in to see coolant temp. ECT was 100°F to start my morning commute vs. I guess it would've been 40°F without the block heater.

The green cold coolant light went off in 0.5 miles from my house vs.2.5 miles on a cold morning like this. (I make it my goal to keep that green cold coolant light on as long a distance as I can from my house because even it seems contradictory I think it means I covered a longer distance on less fuel if it is still green at a certain waypoint than if it already went off before that point!?)

At the end of the first road I take (3 miles from house) I like to see the display just over 60 MPG.This morning it said 74.3 MPG!

Then I have to take a highway where I have to pick up the pace to match the speed of the 'wild idiots' where the MPG will drop until I get close to a town again but the block heater really gave me good head start so to speak.

When I get to work on a cold morning I usually see 60-62 MPG displayed and today it said 69.9 MPG!
(on a saturday with little traffic I am always 70+ despite the cold so still traffic/speed is the biggest MPG killer)

Besides the MPG it is better for the engine not to have to fight the cold!

Why did I not do this sooner? Thanks again for the info posted here guys!

Click on the little blue arrows to read this post in the context of the thread it was originally posted in. I shouldn't make duplicate posts, but I think this one is pretty significant - not only in cold weather but in warmer weather too.

I've been meaning to do this myself. If you do this, please share your experience with us all.

Can anyone chime in on optimum time for plugging in a block heater?
Does it stop at a certain temp?
I have mine on a timer and it switches on about 4hrs before I leave for work.

After a certain amount of time, a block heater won't raise the temperature of the coolant any more.

Here's my observation from using it in a 35 degree garage. If I start the heater 3 hours before I drive the car, that's enough to raise the coolant temperature about 60 degrees above the surrounding temperature. When I start my car, I can see on my Scangauge that the coolant temp is close to 100 degrees. If I leave the heater plugged in longer than a few hours, the coolant temperature won't get any warmer.

If your car is parked outside in the winter, 4 hours is probably a good number to start with...unless the outside temperature is below zero. Then you might want to consider extending that time.

FYI...the little green temperature light on your dash goes off when the coolant temperature reaches 139 degrees. If you don't have a Scangauge, you can figure out how well your block heater is doing by watching how long it takes for that light to go off after you start the car in the morning.

I've seen discussion on here lately about colder temperatures affecting fuel economy. I just wanted to throw in my two cents worth.

The setup: I've got a ScanGauge E that shows exact coolant temp. I live in Central Ohio, where it's been about 10-15 degrees F. I have an engine block heater that I use whenever I can (unrelated to this post, I just love my block heater is all ).

The observation: With the cabin temp set to 68 to 70, and on auto, it eventually ramps up the fan pretty fast. If I leave it on auto, the fan speed stays high, and my coolant temp wont get up to 195F. If it's cold enough, the cabin fan blowing through the heater core pulls enough heat out of the coolant to prevent the engine from reaching full temp.

It would seem to me that an engine not operating at its' optimal temperature, would use more fuel. Might be worth bundling up a little more, turning off auto temp, and lowering the cabin fan speed. Thoughts?

I have driven dozens of times the same 50 km of flat highway, at the same speed (90 km/h) under the same wind conditions, in two directions, with tyre pressure at the prescribed level and with the same person (me) on board. In all cases, the inside temperature was set at 21 C with the heater on Auto. The only difference was the ambient temperature and the fact that in winter I use the front and mirrors and rear defrost at the first 4 km. The first was +15 C and the second was 0 C. I noticed a 15% decrease in fuel economy in the winter on that highway in my Mirage. I am happy with that. It is kind of funny that (if you use Celsius scale) the fuel economy changes by 1% for every degree change in ambient temperature.

Compared to other vehicles I had in the past (with bigger engines) that is very good. The laws of thermodynamics hold, therefore! And, on topic, I see no indication that the heater draws away too much heat from the engine. But these tests were of course not really suited to measure that.

I have driven dozens of times the same 50 km of flat highway, at the same speed (90 km/h) under the same wind conditions, in two directions, with tyre pressure at the prescribed level and with the same person (me) on board. In all cases, the inside temperature was set at 21 C with the heater on Auto. The only difference was the ambient temperature and the fact that in winter I use the front and mirrors and rear defrost at the first 4 km. The first was +15 C and the second was 0 C. I noticed a 15% decrease in fuel economy in the winter on that highway in my Mirage. I am happy with that. It is kind of funny that (if you use Celsius scale) the fuel economy changes by 1% for every degree change in ambient temperature.

Compared to other vehicles I had in the past (with bigger engines) that is very good. The laws of thermodynamics hold, therefore! And, on topic, I see no indication that the heater draws away too much heat from the engine. But these tests were of course not really suited to measure that.

Wow, that's very through, and I would say consistent with my experience. Have you driven well into the negatives though?

Highway driving is passable, that isn't the main issue, though it most certainly could be better. City driving or short drive economy is quite bad, and that's really sad. It's consistently below -10 where i am.

In fact it is now -5 C which is nowadays unusually cold. It used to be colder when I was young (climate change). However, unlike you I enjoy the cold weather a lot when there is no wind. If there is wind, it is really bad. I live very close to the sea, so the air is moist. That gives an extra boost to the cold feeling when windy.